Gulf of Maine Seasonal Sea Surface Temperature Update
Seasonal Patterns in Sea Surface Temperatures
Summer 2024 Highlights
For this seasonal report we present an analysis of sea surface temperature (SST) for summer 2023-2024, defined as the period extending from (June 1, 2024 - August 31, 2024).
Winter is an important time of year for the Gulf of Maine. During this time of year, SSTs are typically falling, weakening the stratification of surface waters from deeper waters that occurs during warmer months. The breakdown of stratification allows for vertical mixing in the water column, which helps transport important nutrients up into the near-surface waters. These nutrients fuel the spring phytoplankton blooms that support the high productivity in the region. Vertical mixing may be enhanced in winter with the help of Nor’Easters, which are most common this time of year and stir up the water column with rough seas and strong winds.
This year, the average SST for the Gulf of Maine was 61.13°F. This seasonal average temperature was 2.03°F above the 1991–2020 climatological reference period (CRP) summer average of 59.1°F.
Weekly Temperatures
Table 1 highlights how the SST for each week this summer compares to the 1991-2020 CRP for the area shown in ?@fig-map. The observed SST, long-term average SST, and SST anomalies (i.e., departures from the long-term average SST) are shown.
summer average SST were on average 2.03°F below normal, with weekly SST anomalies ranging from -1.68°F to +0.41°F; all but one week at the end of 2023 recorded SSTs that were below the 1991-2020 average.
| Table 1. Weekly Average Sea Surface Temperatures - Summer | |||
| (June 1, 2024 - August 31, 2024) | |||
| One-Week Period | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|
Jun 01 - Jun 01 |
54.10°F (12.30°C) |
49.80°F (9.90°C) |
4.27°F (2.37°C) |
Jun 02 - Jun 08 |
54.80°F (12.70°C) |
50.80°F (10.40°C) |
4.04°F (2.24°C) |
Jun 09 - Jun 15 |
55.80°F (13.20°C) |
52.50°F (11.40°C) |
3.25°F (1.80°C) |
Jun 16 - Jun 22 |
58.20°F (14.50°C) |
54.40°F (12.40°C) |
3.78°F (2.10°C) |
Jun 23 - Jun 29 |
57.90°F (14.40°C) |
56.20°F (13.50°C) |
1.64°F (0.91°C) |
Jun 30 - Jul 06 |
58.30°F (14.60°C) |
58.00°F (14.40°C) |
0.33°F (0.18°C) |
Jul 07 - Jul 13 |
61.10°F (16.20°C) |
59.50°F (15.30°C) |
1.61°F (0.89°C) |
Jul 14 - Jul 20 |
62.40°F (16.90°C) |
60.80°F (16.00°C) |
1.58°F (0.88°C) |
Jul 21 - Jul 27 |
63.70°F (17.60°C) |
61.90°F (16.60°C) |
1.87°F (1.04°C) |
Jul 28 - Aug 03 |
64.30°F (18.00°C) |
62.60°F (17.00°C) |
1.69°F (0.94°C) |
Aug 04 - Aug 10 |
64.60°F (18.10°C) |
63.20°F (17.30°C) |
1.45°F (0.80°C) |
Aug 11 - Aug 17 |
65.00°F (18.30°C) |
63.40°F (17.40°C) |
1.61°F (0.90°C) |
Aug 18 - Aug 24 |
65.50°F (18.60°C) |
63.30°F (17.40°C) |
2.16°F (1.20°C) |
Aug 25 - Aug 31 |
64.10°F (17.80°C) |
63.00°F (17.20°C) |
1.13°F (0.63°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | |||
| Climatological Reference Period: 1991-2020. | |||
Monthly Statistics
Table 2 shows monthly average SST for summer 2024. December SSTs were slightly below the 1991-2020 CRP, but the average SST anomalies for January and February were near or more than 1°F below the 1991-2020 CRP.
February showed the largest deviation from the long-term climatological average, with an average SST anomaly of -1.08 °F, making it the 34th warmest February on record. Said another way, it was the 10th coldest February in the satellite era. January averaged –0.94 °F below the 1991-2020 climatology, making it the 25th warmest (19th coldest) January since 1982.
December was more mild, recording a monthly average SST that was 0.13 °F below the long-term average, respectively. This made December the 19th warmest (24th coldest) since 1982.
| Table 2. Monthly Average Sea Surface Temperatures - Summer | ||||
| (June 1, 2024 - August 31, 2024) | ||||
| Month | Rank (1982-2023) | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|---|
June |
2 |
56.60°F (13.70°C) |
53.50°F (11.90°C) |
3.10°F (1.72°C) |
July |
11 |
61.90°F (16.60°C) |
60.50°F (15.80°C) |
1.39°F (0.77°C) |
August |
11 |
64.80°F (18.20°C) |
63.20°F (17.30°C) |
1.64°F (0.91°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | ||||
| Climatological Reference Period: 1991-2020. | ||||
How Does this Summer Compare to the Past?
2024 was the 7th warmest (18th coolest) summer season observed in the Gulf of Maine during the 41 years we have satellite data to analyze, a departure from summer seasons in recent years, which experienced well-above average SSTs.
Seasonal Trends and Long-Term Global Context
The Gulf of Maine is an area of particular interest to the scientific community because of the remarkable rate of warming it has experienced in recent years, coupled with its importance as a major driver for the regional economy.
Figure 2 illustrates the average fall temperature anomaly for each year in the Gulf of Maine since the beginning of the satellite record in 1982 overlaid with long-term SST anomaly trends for the Gulf of Maine (orange) and global oceans (blue) overlaid.
The summer rate of warming for the Gulf of Maine (1.04°F per decade) is roughly ~3.3x as fast as the warming rate for oceans globally (0.27°F per decade).
The summer SST anomaly for the Gulf of Maine in 2024 was 4.29°F cooler than that from 2022, the largest year-over-year decline in summer temperatures in the satellite record.
Marine Heatwave Conditions
The most commonly used definition of a “marine heatwave” (MHW) is when daily average SSTs exceeded the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event. Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 26% of days this summer.
Presenting SST conditions in terms of anomalies ( Figure 4 ) as opposed to absolute values ( Figure 3 ) illustrates in greater detail the magnitude of MHW conditions throughout the summer.
Heatmap of Temperature Anomalies and Heatwave Events
Looking at the full record of daily SST anomalies in the Gulf of Maine (Figure 5), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.
Summer SSTs in the previous 3 years had been noteworthy for their extended MHW conditions, part of the long-term trend of unseasonably warm fall since 2012 (Figure 2). The relatively cold summer in the Gulf of Maine this year were an extension of cooler fall conditions, but stand out against above-average winter conditions since 2012.
Spatial Distribution of Seasonal Anomalies
From an aerial perspective, the Gulf of Maine experienced below-average SSTs during summer of 2024. In general, conditions were cooler in the deeper-water basins and warmer in shallow protected areas like the Bay of Fundy and Massachusetts Bay. The highest seasonally averaged SST anomaly in the Gulf of Maine was 2.29°F - located near the Bay of Fundy.
Monthly Temperature Anomalies
Average monthly SST anomalies are shown in Figure 7.
About the Updates:
Over the past decade, scientists have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To help keep you informed, we share seasonal and annual updates about conditions in the Gulf of Maine. For a full compilation of all of GMRI’s seasonal and annual Gulf of Maine warming updates, visit: https://gmri.org/warmingupdates/.
The Gulf of Maine Region
For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (?@fig-map), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is outlined with the dashed line below. This area is consistent with previous seasonal and annual SST reports that scientists at GMRI have produced.
Data Sources:
NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.
Citing This Work
If you would like to cite this report, please use:
Gulf of Maine Research Institute. 2024. Gulf of Maine Warming Update: Summer 2024
Note About the Data:
The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.
Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.